Validate LinkWalletDto address format with an Ethereum address validator

[dDevAhmed]

Overview

Wallet address only validated as non-empty string.

Why it is a problem

Cryptic errors and invalid data stored.

Expected behavior

Reject invalid Ethereum addresses early.

Current incorrect behavior

Any string accepted.

Suggested fix

Add @Matches(/^0x[0-9a-fA-F]{40}$/) or custom @IsEthAddress.

Acceptance criteria

Invalid address returns 400 with friendly message.

Complexity

Low